<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <meta name="viewport"
    content="width=device-width, initial-scale=1, maximum-scale=1,minimum-scale=1, user-scalable=no" />
  <title></title>
  <link rel="shortcut icon" href="../favicon.ico" type="image/x-icon" />
  <style>
    .ct {
      width: 30px;
      height: 30px;
      background-color: #ddd;
      border-radius: 50%;
      box-shadow: 0 0 0 30px transparent;
      transition: all 0.3s ease-in-out;
      /* animation: shadows 1s ease-in-out infinite; */
    }

    /* @keyframes shadows {
      0% {
        box-shadow: 0 0 0 30px transparent;
      }

      50% {
        box-shadow: 0 0 0 0 #ddd;
      }

      100% {
        box-shadow: 0 0 0 30px transparent;
      }
    } */

    .ct:hover {
      box-shadow: 0 0 0 0 rgba(255, 255, 255, 0.2);
      transition: all .4s ease-in-out;
    }

    .box {
      background-color: #1691BE;
      padding: 100px;
    }
  </style>
</head>

<body>
  <div class="box">
    <div class="ct"></div>
  </div>
</body>

</html>